A wireless power transmission system wirelessly transmits power from a power transmission device to a power reception device. The power transmission device includes: a commercial AC power supply; an AC/DC converter that converts AC power to DC power; a DC/DC converter that converts an output voltage of the AC/DC converter to an arbitrary voltage; an inverter that generates high frequency power from output power of the DC/DC converter; and a resonator (power transmission resonator) that generates a magnetic field according to the high frequency power. The power transmission resonator includes a coil and a capacitor. The high frequency power includes a resonant frequency of the power transmission resonator. This realizes efficient transmission. The power reception device includes: a resonator (power reception resonator) that receives power through the magnetic field transmitted from the power transmission resonator; a rectifier that converts the AC power obtained by the power reception resonator to DC power; and a DC/DC converter that converts an output voltage of the rectifier to a voltage according to a battery. A pair of the power transmission resonator and the power reception resonator will be referred to as a resonator pair. The power reception device is connected to the battery, and the output voltage of the DC/DC converter is supplied to the battery. In the wireless power transmission system, the power is propagated through the magnetic field radiated into a space, from the power transmission resonator toward the power reception resonator. Strength of the radiation magnetic field (leakage magnetic field) needs to be equal to or smaller than a value compliant with laws and regulations represented by the Radio Act.
An example of a known technique for satisfying the requirement includes a technique of using a plurality of power transmission systems and a plurality of power reception systems to adjust a phase relationship between currents of the power transmission systems to cancel out, at an arbitrary distant place, magnetic fields radiated from the plurality of power transmission systems. However, when there is a difference between coupling coefficients of the resonator pairs, amplitudes of the currents of the power transmission resonators vary, and the radiation magnetic fields cannot be canceled out. To improve this, the output voltages in the DC/DC converters of the transmission systems and the output voltages of the rectifiers in the power reception systems need to be changed according to the coupling coefficients. However, this complicates the process, and there is a problem that a convergence of control is reduced.